A vehicle wheel includes a tire and a rim. The tire is mounted on the rim by the beads of the tire fitting onto the rim. Close contact between the beads and the rim allows hermetic seal. The fitting of the beads onto the rim is very significant for the wheel.
The rim is fastened by the beads fitted on the rim. The tire is fixed to the rim by the fastening force. When a vehicle is quickly accelerated or decelerated, a great force is generated in the circumferential direction between the rim and the bead. If the fastening force of the bead is insufficient, the rim may slip on the bead, which is called “rim slip.” If rim slip occurs, the transmission of a force from the vehicle body to the road surface or from the road surface to the vehicle body is inhibited. This leads to decrease in steering stability. Further, rim slip may cause mass balance of the tire to be reduced. This leads to vibration of the vehicle during traveling. Moreover, the insufficient fastening force of the bead may cause separation of the bead from the rim when the vehicle turns, and this may cause “separation from rim”.
If the bead is designed to have a great fastening force, rim slip and separation from rim can be reduced. However, if the bead has great fastening force, it is necessary to exert a high fitting pressure in order to fit the beads onto the rim. Time and effort are required to mount such a tire onto the rim. For such a tire, the bead may be locally twisted due to an influence of the high fitting pressure. The twisting may lead to imperfect fitting.
JP2013-151198 discloses a tire in which the fitting pressure is reduced while the fastening force of the beads is maintained. In this tire, the core of the bead includes two kinds of bead wires having different elongations.